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A185239 Numbers n such that (11^n + 10^n)/21 is prime. 4
53, 421, 647, 1601, 35527 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are prime.

a(6) > 10^5.

LINKS

Table of n, a(n) for n=1..5.

MATHEMATICA

Select[ Prime[ Range[1, 100000] ], PrimeQ[ (11^# + 10^#)/21 ]& ]

PROG

(PARI) is(n)=ispseudoprime((11^n+10^n)/21) \\ Charles R Greathouse IV, May 22 2017

CROSSREFS

Cf. A057178, A128341, A181141, A187819, A217095, A213216.

Sequence in context: A244771 A074836 A142851 * A053736 A181968 A261537

Adjacent sequences:  A185236 A185237 A185238 * A185240 A185241 A185242

KEYWORD

nonn,more

AUTHOR

Robert Price, Apr 05 2013

STATUS

approved

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Last modified May 25 04:50 EDT 2019. Contains 323539 sequences. (Running on oeis4.)